JPS6339655B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy sheet that is primarily used for packaging, but can also be used for other applications when manufactured to an appropriate thickness. For aluminum alloy sheets to be formed into products judged by surface appearance, it is important that the grain size is small. Today, even crystals as large as 200 microns are considered commercially acceptable as sheets. However, sheets with grain sizes in the range of 50 to 70 microns are highly preferred for their superior appearance. Although the present invention will mainly be described with respect to a sheet for manufacturing bottle closures, which needs to be a 0.15-0.25 mm thick sheet, the present invention is also applicable to press-formed parts of kitchen appliances. 3
It is applicable to sheets from mm thick to 15 micron thick for very thin aluminum foils. Large amounts of aluminum alloys are used for the manufacture of bottle closures and similar applications, such as for the manufacture of can ends and foil containers. For bottle closures, it is necessary to have good lacquer adhesion, sufficient strength to withstand the forces generated by carbonated beverages, and good moldability. This is because closures made from sheets come into contact with liquids, especially beverages. Of course, if the required lubricity and formability are similarly obtained, substantial savings can be made by increasing the strength of the alloy over other alloys used for the same purpose. can. This is because a smaller gauge (thinner thickness) sheet can be used to perform the same function. for example,
Reducing the thickness by just 0.01 mm (approximately 4%) can result in significant savings in the manufacture of bottle closures and other similar products. Similar savings could be realized if costly, long-term, high-temperature heat treatments could be eliminated. As is well known, the presence of magnesium oxide in the oxide surface layer of aluminum reduces the lacquer adhesion of the aluminum alloy sheet. Therefore, it is common practice to limit the magnesium content of Al alloys for packaging to the level of impurities. Therefore, the Mg content of many known alloys for packaging is generally below 0.05%.
Such an alloy is considered to be Mg-free, and the aluminum alloy according to the present invention is also such an alloy. Bin closures are often printed on the outside. Such printing is performed on a flat sheet prior to punching out individual closure blanks from the sheet and drawing them into closures. Unloading prevention type (pilferpsoof)
In the case of deep-drawn closures (type), in order to prevent the printing from being excessively damaged during the drawing process, the earring value indicated by the sheet must be 2%.
It is important not to exceed. However, this is less important in the case of shallow closures where the edges are not printed. Larger earring values may also be used in the case of clip-on type shallow closures, and also in the case of shallow containers such as those used for packaging individual portions of food. The I Young value exhibited by an aluminum alloy sheet is determined by the alloy composition as well as by the conditions under which the sheet is manufactured from an initial as-cast or hot-rolled slab. In particular, the earring value at 45 degrees to the rolling direction increases as the cold reduction rate increases during temper rolling, that is, during cooling rolling, which is applied after the final annealing treatment to increase strength. There is a tendency to For packaging purposes, particularly for the manufacture of bottle closures, it is desirable to be able to process the alloy to exhibit low earring values after being subjected to high finishing reductions (30% or more) by temper rolling. According to the present invention, the aluminum alloy sheet contains Fe: 0.6-1.0% Si: 0.5-0.9% Cu: 0.3-0.5% Mn: less than 0.3%Ti+B: amount required for conventional crystal refinement (Ti+B 0.006-0.06% ) Other: Made from an aluminum alloy having a composition consisting of not more than 0.15% in total and the remainder not exceeding 0.05% in each case. Preferably, the contents of Fe and Si are each
It should be within the range of 0.6 to 0.8. Fe
The total content of and Si is preferably 1.6% or less,
More preferably, it should be within the range of 1.30 to 1.50%. When the Fe+Si content exceeds 1.6%, the earring value increases accordingly.
The Fe/Si ratio is controlled to control grain size.
It is preferable to set it to 1.00 or more. This Fe/Si ratio is
It should not be less than 0.9 and preferably not more than 1.4. The Mg content is preferably 0.02% or less in order to completely eliminate the need for surface treatment to remove surface oxides prior to lacquer coating.
More preferably it is 0.01% or less. Manganese is preferably present in an amount of no more than 0.2% and usually no more than an impurity amount (less than 0.05%). However, for alloys where relatively large grain sizes are of minor importance, improving the strength of the alloy requires
It may be desirable to add manganese in amounts of 0.3% or less. Aluminum alloy sheets for bottle closures are manufactured from alloys containing 1% Mn and 0.3% Cu, usually with the addition of a small amount of chromium, as is already well known. However, in such alloys, the ingot is subjected to an extended homogenization heat treatment prior to hot rolling in order to ensure that the final cold rolled sheet has sufficiently small grain sizes and low earring values. It is necessary to do this. The alloy according to the invention has similar strength and earring values to known sheets, but is easier to manufacture since it is not necessary to homogenize the ingot to achieve an acceptable grain size. A certain alloy sheet is obtained. It is already well known to produce aluminum alloy sheets containing 0.75% Fe and 0.75% Si. This material, when produced by temper rolling suitable for the manufacture of closures by deep drawing, has substantially less strength than the alloy sheet of the present invention, and is therefore not suitable for such purposes. It cannot be compared with other products. When compared with known Al-Mn-Cu alloys, the present invention has a lower Mn content, which results in smaller grain sizes and increases the earring value even after temper cold rolling. It is possible to further reduce the grain size without causing any damage. As the Mn content of the alloy according to the present invention increases from an impurity level of 0.05% or less to 0.2 to 0.3%, the grain size and earring value increase somewhat, but the reduction rate by final skin pass rolling is kept constant. There is an advantage that the tensile strength is improved when this is done. When manufacturing bottle closures, it is important that the sheet has consistent strength throughout. Materials that are stronger than a certain strength present difficulties in manufacturing and also in the use of bottle closures, particularly anti-unloading bottle closures. In the manufacture of bottle closures (and other products formed by drawing circular blanks), a significant amount of scrap is generated due to the stamping of circular blanks from sheets. This scrap is generally returned to the sheet manufacturer. When the number of alloying components is small, it is much easier and therefore less expensive to maintain uniform quality, especially when using large amounts of return scrap. Fe for aluminum alloys
Considering that it is necessary to constantly control the content of , only requires the addition of Cu and is therefore more advantageous than known alloys in that respect. This is also one of the reasons why it is preferred that the Mn content of the alloy according to the invention be less than 0.1%. Al−Fe−Si with added Cu as in the present invention
The alloy was investigated experimentally in the laboratory using a 63.5 mm thick DC ingot. The ingots used were rolled by a method designed to simulate the homogenization and rolling operations employed to commercially produce closure stock from manganese-containing Al alloys. 2 used
The seed alloys are as follows.

[Table] These materials were treated at 610℃ for 9-10 hours, cooled to 570℃, hot rolled to 19mm, heated again to 450℃, and then hot rolled to 3.6mm. Rolled. This simulated the method used for known Al-Mn 1% alloys. The temperature of the slab at this point is approximately
It was 170℃. In other words, the temperature was much lower than that during rolling that is generally performed. After cold rolling to 0.91mm, the material is
Annealed at 380°C, cold rolled to 0.33 mm, reannealed, and finally cold rolled to 0.23 mm after annealing. This corresponds to a cold reduction rate of approximately 30%. The final sheet material strength, earring value and grain size are shown in the table below. The properties of three known alloys are also shown; these are Al-
They were temper rolled under approximately the same conditions, except for the Fe-Si alloy, and underwent the same homogenization treatment prior to hot rolling.

[Table] As shown in the table above, adding approximately 0.4% Cu to a known Al-Fe-Si alloy strengthens the alloy.
In that case, many of its properties are known Al-1%Mn
Close to alloy properties. However, even with the homogenization treatment, it was not possible to reduce the grain size of the Al-1%Mn alloy to a desirable level. The effect of adding Cu to known Al-Fe-Si alloys appears to be to increase the strength of cold rolled sheets by at least 10% while retaining favorable earring values and fine grain sizes. It can be done. Therefore, a reduction of about 10% is possible without causing a loss in overall strength. When Cu is added in amounts less than 0.3%, the increase in strength is small and the product is not strong enough to compete with other known products with desirable low earring values and small grain sizes. I can't say that. Cu
When the content is increased to 0.5% or more, the formability and corrosion resistance of the alloy decrease. When alloy C1 is tempered to H.15 or H.16 by increasing the cold reduction rate to approximately 40% and 50%,
UTS respectively under laboratory conditions as described above.
It was expected that the pressure would increase to 179MPa and 183MPa. Temper rolling with increased reduction increases the 45° earing value, but at lower hot rolled slab temperatures such as those used in the laboratory, the 45° earring value increases compared to commercial rolling conditions. It is known that earring values are particularly noticeable. Therefore, even at a large reduction rate of 40 to 50%, the earring value still remains at a maximum of 2%.
expected to be within the range of This was confirmed through further experiments. These experiments were conducted on a larger scale, and the alloy specifications at that time were as follows.

Table: The ingots used in this experiment were full size commercial rolling ingots. After scalping, the ingot was heated and held at a temperature of 570-580°C for 6 hours to ensure temperature uniformity prior to rolling. This means that Al-1%Mn
The usual method of homogenizing the alloy is 12 to 590-625℃.
In contrast, it holds for ~70 hours. The ingot was then hot rolled into hot mill coils 3-4 mm thick. Furthermore, this hot mill coil was subjected to finish skin-pass rolling at rolling reductions of 40% and 50%, respectively, and cold-rolled to a thickness suitable for closures. The heating applied to the ingots prior to hot rolling is representative of the heating methods conventionally used to ensure that large ingots are brought to a uniform temperature. , and is typical of the heating process applied to unalloyed aluminum ingots prior to hot rolling. The properties obtained were as follows.

[Table] The above properties were obtained before applying lacquer to the sheet. Since heating in a furnace is generally performed after coating the lacquer, a certain degree of annealing is performed and the strength of the sheet is reduced. This type of alloy may be used in other applications that require even greater strength but are not necessarily required to have such good earring values, so they are subjected to more severe skin-pass rolling. It was. For this purpose, a sample of hot rolled coil was subjected to four rolling rounds selected for the experiment. They were as follows. A: Cold rolled to 1mm (0.040 inch), annealed,
Cold rolled to 0.37mm (0.0145 inch), annealed and temper rolled to 0.22mm (0.0087 inch). B Cold rolled to 1 mm (0.040 inch), annealed,
Cold rolled to 0.23mm (0.009 inch). C Annealed, cold rolled to 0.23 mm (0.009 inch). D Cold rolled to 0.23 mm (0.009 inch) without annealing. Method A was to carry out the aforementioned large-scale experiment for performing H.15 temper rolling. Annealing is 380
The reaction was carried out for 2 hours at ℃. One sample from the end and one sample from the center of the hot rolled coil was rolled by each method. Tests for earring value and tensile strength were performed on the final size material. Grain dimensions were determined for Methods A, B and C either at the final annealing step or after some cold rolling as in Method C. Also,
The materials obtained by Methods C and D were subjected to a rather severe furnace heat treatment after lacquer application prior to being subjected to tensile testing.
Treated at 205°C for 20 minutes. The results of the test are shown in the table below. The strength increases gradually with increasing cold rolling reduction, as expected. However, in the case of methods C and D, there was almost no difference in mechanical properties between the material annealed at the hot rolled coil stage and the material not annealed. The amount of 45 degree earring value increases by performing cold rolling, but as can be seen from the table,
The increase varies approximately linearly with the extent of cold rolling, expressed as rolling true strain. As can be seen by comparing method D, which anneals hot rolled coils, the earring value decreases only slightly as in method C. The grain sizes are all small, and as expected, the largest one is the one annealed at the hot-rolled coil stage, and the grain size is approximately 50~
It was 70 microns. Both Method A and Method B resulted in finer grain sizes compared to commercially produced materials for bottle closures. The properties obtained are summarized in the table below.

【table】

[Table] As can be seen from the data in the table above and the experiment described above, as long as it is desired to keep the earring value below 2% or not significantly exceeding it, the final temper rolling reduction can be It should not significantly exceed 50% (should be about 60% or less). The reduction rate due to this temper rolling is
To obtain a minimum UTS of 150 MPa, 30
It should not be significantly less than %. However, in cases where strength is more important as opposed to a low earring value, for example in the case of household aluminum foil, it is preferred to carry out skin pass rolling with a rolling reduction of more than 80%. Sheets made from the different compositions disclosed herein all have grain sizes substantially below commercially acceptable limits, and in fact all exhibit grain sizes of less than 100 microns. It is noted here that in methods A and B, the hot rolled slab is not heat treated prior to starting cold rolling, and annealing is performed one or more times at an intermediate stage of the cold rolling schedule. It's summer. The initial annealing treatment used in Method C had little benefit compared to Method D. The sheet according to the present invention is of a work-hardening type, and in its manufacture, no heat treatment for precipitation is performed after hot working. Subsequent heat treatments are limited to intermediate annealing for recrystallization to control the earring value and softening to reduce work in the subsequent cold working step. If the earring value is of little importance, the article may be manufactured without an annealing step, as can be seen from the above results. All alloy composition percentages and ratios herein are by weight. The method for producing alloy sheets according to the invention has been described by way of example in the production of such sheets on a commercial scale from conventional rolling ingots. The thickness of such commercial ingots is such that it is necessary to substantially reduce the thickness by hot rolling prior to reduction by cold rolling.
The alloy for producing the sheet according to the invention, however, can be simply cold rolled by utilizing various strip casting machines (continuous casting machines), such as the well-known Hunter type double roll strip casting machine. It can be cast to a thickness sufficient to allow rolling. Typically 5-8 mm for such casting equipment.
A cast strip with a thickness of . The cast strip of the alloy according to the invention thus obtained can be rolled to any desired thickness by reduction by cold rolling alone and without precipitation heat treatment of the cast strip. It may be desirable to carry out a conventional recrystallization annealing treatment prior to and/or during cold rolling of the cast strip.

Claims (1)

[Claims] 1 Fe 0.6-1.0% Si 0.5-0.9% Cu 0.3-0.5% Ti+B Amount required for conventional crystal refinement (Ti+B 0.006-0.06%) Others The total does not exceed 0.15%, and Aluminum alloy sheets made from alloys each having a composition with the balance not exceeding 0.05% aluminum. 2 Fe 0.6-1.0% Si 0.5-0.9% Cu 0.3-0.5% Mn 0%-0.3% Ti+B Amount required for conventional crystal refinement (Ti+B 0.006-0.06%) Others The total does not exceed 0.15%, Aluminum alloy sheet made from an alloy having a composition in which each part has a composition not exceeding 0.05% aluminum, and the balance not exceeding 0.05% aluminum.